Simulation of defect interactions in binary/ternary group IV semiconductor alloys at the density functional theory level is difficult due to the random distribution of the constituent atoms. The special quasirandom structures approach is a computationally efficient way to describe the random nature. We systematically study the efficacy of the methodology and generate a number of special quasirandom cells for future use. In order to demonstrate the applicability of the technique, the electronic structures of E centers in Si-1 Ge-x(x) and Si-1 (x) yGexSny alloys are discussed for a range of nearest neighbor environments. (C) 2010 Elsevier B.V. All rights reserved.